It is often desirable to obtain image data of an area of interest and transmit the image data to a person having specialized knowledge, who can then review the image data and make a final decision on the basis of such review. Such transmission of image data is desirable in many civilian and military applications. For example, it may be desirable to transmit the following types of images to a remote location for review: medical images (teleradiology), archived scientific images, fingerprint and forensic images, images captured by spacecraft, satellite images of Earth, unmanned vehicle images, security camera output, air and vehicular traffic control images, military reconnaissance images, battlefield inspection images, and remote targeting images.
In prior art systems, a collected image was most often collected and transmitted automatically, according to a predetermined protocol. In transmitting image data, it is necessary to provide a remotely located reviewer with an image of sufficient detail so that the desired information can be extracted. Therefore, an image is normally broken down into a very large number of picture elements or "pixels" and transmitted over a communications channel. Unless the channel has a particularly high channel capacity, the transmission of a detailed image in this manner can take a significant amount of time, and as a result the cost of delivery will be increased.
To reduce image transmission time, earlier systems used data compression techniques. Data can be compressed in a lossy form (i.e. some information is lost due to compression) or in a lossless form in which no original image information is lost in the compression and subsequent expansion process. U.S. Pat. No. 4,903,317 to Nishihara et al. shows an image processing apparatus for medical diagnosis that uses both lossy and lossless compression in a Huffman code technique. The Nishihara patent shows a circuit with a memory for storing image data, a loss-compression circuit, an expansion circuit for expanding the loss-compressed data, and a difference circuit for calculating the difference between the original image data of the image memory and the expanded image data of the expansion circuit. The difference data is lossless-compressed and combined with the lossy-compressed main data to produce a combined compressed data set that can be transmitted or stored, and later decompressed without any loss of original image information. However, Nishihara does not provide any sequential transmission of differently-compressed data or any interaction between a remotely located expert and the compression and transmission system.
Another earlier system allowed a transmitting operator to vary the resolution of the image being transmitted. U.S. Pat. No. 5,128,776 to Scorse et al. shows a prioritized image transmission system for processing and transmitting video imagery. The operator of the imaging system selects desired portions of the video image for transmission to a remote reviewer with operator-selected levels of resolution, compression and order of transmission. The Scorse-type system is further discussed in the March, 1993 issue of Advanced Imaging Magazine in an article by James Scorse titled "Sending Images Through the Air: Image Transmission by Radio." Like systems of the Nishihara type, the Scorse-type system does not permit the remotely located expert to control the acquisition or the detail level of the information being transmitted to minimize the amount of data that must be transmitted.
U.S. Pat. Nos. 4,682,869 to Itoh et al.; 4,870,497 and 4,979,049 to Chamzas et al.; 4,999,715 to Porcellio et al.; 5,166,987 to Kageyama; 5,189,526 to Sasson; and 5,204,756 to Chevion et al. show other systems performing image transmission or compression functions.
In his study of image data transmission techniques, the inventor has identified a need for a system that radically decreases the transmission time and cost of transmitting images for remote analysis. Since typically only a small portion of any image is of significant interest to the reviewer, accurate transmission of the entire image is not necessary. However, none of the prior art systems make use of the knowledge of the expert (end user) receiving the image to maximize the efficiency of image transmission.